MOPED ARMY

I'd have to get a new intake I think. Not super easily. But can Gurtnet jets be found anywhere? Should I avoid downjetting?

Put a delorto on there dont mess with that gurtner crap...make sure timing is correct...I have found that advancing timing a little more than stock is better performance overall ...if you must stay with gurtner you can use micro drill bits to get a measurement ...even a 12/14 delorto works better than a gurtner. find a cable choke one to retain handle bar control..that ped should cruise 30-35...

float might be set too high

It's possible that it's actually running too lean with all of that work you've done. Lean four stroking sounds very similar to rich four stroking. Throw a new spark plug on there, take it for a wide open throttle run and check the plug color.

Two things: the float is stuck and the carb is pouring gas out OR the engine has very little compression left and just cant burn all the gas (so when you cut the fuel you get a burst of speed when it can handle the gas)

Well, bad piston rings would do it, they may not look bad when you took them off but can still be. Also, not sure if your ped comes with a decompressor, but that valve not closing all the way or having a bad seal would give you bad compression...

I could be wrong, your problem may be something else. I would do a compression test on the motor, take it to a local autoparts store and they will do it for free if you dont have a gauge. If the compression is ok its something else. If the comp is bad and the rings are new, then its most likely the valve, there are a few ways to seal those. I would then take the head off and check the valve. Best way for me was to aim the head at a very bring light and see if any light comes through around the decomp valve on the other side. If it does its not sealing. Then you take the valve off and see if its the valve or the head thats damaged. If its the valve, get a new one. If its the head, you can get a buildup material and make a new seal (same stuff used on valve jobs in a car). Sometimes you can just adjust the tension and it will seal. But check the compression first, so you dont end up doing a bunch of empty work...

wait, maybe you mean the hole that opens when you pull the decompressor?

Got it, I'll check for valve leaks and go for a comp test. I bought the rings from moped junkyard, so there is a slight possibility I've been ripped off, but I'll try new rings last to avoid spending too much money.

I'll do a plug chop too. I replaced the plug in January and by February it was carbon fouled, although after taking everything apart the carb and engine were really clean so perhaps it was just fouled from running rich?

Gurtners have removable jets. I bought a #54 (down from a #60), hope that's not too lean. Everyone talks shit about them but mine is probably 15 years old and it was clean as a whistle when I took it apart. I also didn't see all those tiny little holes that fill up with stuff like everyone says. Maybe the Motobecane Gurtners (which are a different design) are less forgiving.

Thanks so much for all the advice!